Closure means for furnace vestibule



July 26, 1966 CLOSURE MEANS FOR FURNACE VESTIBULE 2 Sheets-Sheet 1 iii ki 7 Zq if 2 i III- 1 I Z8 E1 5 i7, I /q INVENTORSI 4 1| H hi ALFREDEPARKEE.

22 TIE-- HENRY I/I T E/JHHAMM.

fi i QM 'ATTys.

y 1966 H. w. SCHRAMM ET AL 3,262,407

CLOS URE MEANS FOR FURNACE VESTIBULE 2 Sheets-Sheet 2 Filed Feb. 5, 1964m w L mam T L mEH M EKG .7 5, 5 PW I am 4 H \PM I \I\ J Z A VH r 4 B Mlilllllllllll'lllllllll" United States Patent 3,262,407 CLOSURE MEANSFOR FURNACE VESTIBULE Henry W. Schramrn and Alfred G. Parkes, Toledo,Ohio, assignors to Midland-Ross Corporation, Toledo, Ohio, a corporationof Ohio Filed Feb. 3, 1964, Ser. No. 341,988 Claims. (Cl. 110-173) Thisinvention relates to improved closure means for a furnace vestibule andparticularly for vestibule of a furnace adapted to contain a combustiblemetallurgical treating atmosphere.

In the heat treating of metal work pieces in a combustible treatingatmosphere, as in the carburizing of ferrous metal work pieces in acarbonaceous atmosphere, it is customary to provide the inlet to thetreating furnace with an antechamber, usually called a vestibule. Workpieces to be treated in the furnace are initially charged into thevestibule which initially is sealed from the furnace by means of a door.After the work pieces are inside the vestibule, and prior to the timewhen they are transferred into the furnace treating chamber, theentrance to the vestibule is closed byclosing means, such as a door.Then the vestibule is purged by continually adding fresh treatingatmosphere thereto, as is commonly accomplished by permitting acontrolled leakage of atmosphere from the furnace treating chamber tothe vestibule, while simultaneusly venting atmosphere from an efiluentof the vestibule. The purpose of the purging step is to rid thevestibule of the air which will unavoidably pass thereinto when the doorto the vestibule inlet is open to permit the entry of workpieces, sothat air does not subsequently enter the furnace treating chamber.

The closure means heretofore frequently provided for closing the inletto the vestibule when it is not desired to pass work pieces therethroughcomprises a stationary substantially flat annular plate attached to thevestibule casing and circumscribing the vestibule inlet, and asubstantially fiat door plate of sufiicient extent to cover the openingof the annular plate and movable into and out of abutting relationshipwith the annular plate. In such an arrangement the inlet to thevestibule is nominally sealed by the continuous annular plane of contactbetween the stationary substantiallyflat annular plate and asubstantially flat annular portion of the door plate when the door is inabutting relationship to the annular frame.

Closure means according to the above have not always provensatisfactory, however. In a number of instances, it was known that thecontinuous seal between the annular plate and the abutting annularportion of the door plate was broken due to warpage or bending out offlatness of the annular plate and/or the door plate. Since a surfacevestibule is normally maintained at a slight positive pressure toprevent the influx of air, a break in the continuity of the seal at theinlet to the vestibule will permit atmosphere gases from the vestibule,which frequently contain carbon monoxide, to escape into the air.

Accordingly, it is the object of this invention to provide closure meansfor a furnace vestibule opening which can limit to an acceptable levelthe escape of gases from the vestibule when the opening is closed,notwithstanding some warpage or bending of various elements of theclosure means.

F or a further understanding of the invention, attention is directed tothe following portion of the specification, the drawing, and theappended claims:

FIG. 1 is a fragmentary elevational sectional view of a furnacevestibule embodying closure means constructed in accordance with thepresent invention;

FIG. 2 is a front elevational view of the closure means taken on line 22of FIG. 1, with portions thereof broken away to show various details ofconstruction;

3,262,407 Patented July 26, 1966 ice FIG. 8 is a fragmentary frontelevational view of the closure means of FIG. 7, taken on line 88thereof; and

FIG. 9 is a fragmentary elevational sectional view of a modification ofthe embodiment of FIGS. 7 and 8.

Referring now to FIG. 1 of the .drawing there is shown Wall means '11defining a vestibule 12 which serves as an antechamber to the treatingchamber of a metallurgical heat treating furnace (not shown) in acustomary manner. Vestibule 12 is provided with an opening 13 throughwhich workpieces may be added from and/or'removed to an exterior worksupport table 14. Work support means such as roller rails 15 areprovided within verstibule 12 for supporting the workpieces therein.- Inthe illustrated embodiment, work support table 14 is shown as comprisingsimilar roller rails 16 aligned with roller rails 15 to permit workpiececarries (e.g. a furnace tray or basket) to be rolled into and/ or fromthe vestibule without the need for a lifting device.

The vestibule illustrated in FIG. l is applicable to batch type furnacesof a popular style in which a workpiece quenching station 17 is disposedsubjacent the vestibule in the manner described in US. Patents 2,940,619and 2,898,101. However, it is contemplated that the invention possessesutility in connection with vestibules of other types of batch furnacesand in connection with the inlet and/ or outlet vestibules of continuoustype furnaces.

Opening 13 to vestibule is circumscribed by an annular member, showngenerally at 18, which is attached to wall means 11. Annular member 18comprises a plate 19 having a generally flat annular face 21. Duringperiods when it is not desired to introduce or remove workpieces fromvestibule 12, as the case may be, opening 13 is closed by lowering avertically reciprocable door, shown as comprising a generally flat plate22, into position in front of opening 13. Door 22 is of sufiicientextent to have a generally flat annular surface portion 22a (FIGS. 4 and5) adapted to abut against the'face 21 of plate 19 when door 22 islowered and to form a continuous annular seal therewith. Thereciprocation of door 22 into and out the closed position isaccomplished by means of a hoist mechanism 23 which may be manually ormechanically actuated. In its closed position door 22 is biased againstplate 19 in customary fashion when wedges 24 carried by door 22 contactrollers 25 attached to wall means 11.

In the prior art it was common to attempt to seal a furnace vestibule bymeans of an annular seal such as that obtained between annular surface22a of door 22 and annular face 21 of plate 19. Such prior installationswere, however, plagued by serious disruptions in the continuity of theannular seal resulting from warpage orbending of one or the other of theconstituent sealing members, viz.-members corresponding to door 22 andplate 19. Previously, attempts have been made to eliminate or minimizethe effect of these disruptions by carefully machining the abuttingfaces of the sealing members to a high degree of flatness and by stressrelieving one or both of the sealing members. Also, it has been known touse unusual materials in the construction of the sealing members, suchas the use of ooreplate in the construction of the vestibule door. Noneof these expediencies, however, alone or in combination, has beeneffective to provide a vestibule closure seal of sufficient quality tomaintain the rate of leakage of atmosphere gases from the ves- =2 tibulewithin acceptable limits in every case. Even in the case of designs thatwere heretofore relatively superior a number of the furnacesmanufactured according to such a design would develop excessive rates ofatmosphere leakage in service. These furnaces could not always besatisfactorily repaired, and when they were repaired, it was usually atconsiderable expense since it was usually necessary to send a fieldengineer from the manufacturers office to the customers plant tosupervise the repair work.

According to this invention, however, it is possible to simply andrapidly correct serious disruptions in the con- .tinuity of the sealbetween annular face 21 of plate 19 and annular surface 22a of door 22.This is accomplished by providing a plurality of adjustment meansdisposed around one or the other of annular face 21 of the vestibule andannular surface portion 22a of thedoor for biasing localized portions ofthe one or the other face or surface portion out of its normal position(usually out of relatively true flatness) to close any localized gapwhich may develop between the abutting surface.

In the illustrated embodiment the adjustment means are carried byannular member 18 of the vestibule and comprise a plurality of biasingmeans 26 disposed at spaced loci in an annular pattern circumscribingopening 13 to vestibule 12. In a typical installation, the spacingbetween adjacent biasing means may be of the order of 4 to inches. Eachbiasing means 26 comprises a stud 2'7 securely mounted in annular plate19 and extending transversely therefrom toward the vestibule. Stud 27slidably passes through the bore of an annular bolt 28 and a nut 29 isthreaded on the external end of stud 27. Annular bolt 28 is threadedthrough a tapped aperture in an annular member 31 which is secured towall means 11 of vestibule 12. The end of annular bolt 28 is slidablyadapted to bear against the back of plate 19 (or against a member suchas a washer 33 in contact therewith).

Annular plate 19 is maintained in a spaced relationship with respect toannular member 31 and the space therebetween, typically of the order ofthree-eighths inch, is packed with resilient sealing means, preferablymoder-- ately heat-resistant, such as spaced apart strands of asbestosrope 32, to prevent the escape of atmosphere gases from the vestibuletherethrough.

Whenever a gap occurs between the frame and the door, the plate 19 islocally moved toward or away from the door to close the gap. In makingthis adjustment, both the annular bolt 28 and nut 29 holding stud 27 inposition are moved. When a gap occurs by a concave bow along theengaging surface 22a of the door 22 or along frame engaging surface 21,nut 29 is loosened on stud 27 to permit the annular bolt 28 to betightened to'thereby force the frame engaging sufiace 21 toward doorengaging surface 22a to close the gap. Nut 29 is only loosened enough topermit this adjustment and both washer 34 and washer 33 are incompression after adjustment. Adjacent means 26 would be moved in theopposite direction, i.e. nut 29 would be tightened drawing stud 27 andframe 19 up; annular bolt 28, of course, must be loosened to permit thisadjustment.

FIGS. 7 and 8 illustrate an embodiment of the invention which issomewhat simpler in construction than that illustrated in FIGS. l-6.According to' this latter embodiment, an opening 113 to a vestibule 112is circumscribed by an annular member 118 which is attached to the wallmeans 111 which serve to define vestibule 112. Annular member 118comprises an annular plate 119 which may be non-adjustably assembledwith the other constituent elements of member 118. Opening 113 may beclosed by vertically reciprocable door 122 which may be operated in themanner of door 22 of FIG. 1. Door '122 is provided with an annularchannel 141 which is adapted to be aligned with annular plate 119 andwhich is disposed with the channel opening facing toward annular plate119.

The opening of channel 141 is filled with packing 142 of t moderaterigidity which extends toward plate 119 beyond the limits of channel 141and which is backed up by a thin flexible metal plate 145. A braidedgroove packing available from Johns-Manv-ille Company under theirdesignation #JM872 is suitable for packing 142. A seal between door 122and annular member 118 is, therefore, obtained when annular face 142a ofpacking 142 is biased against annular face 121 of member 119, as bymeans of Wedges and rollers (not shown) in the manner of elements 24 and25 of FIG. 1.

Any localized gap which develops as a result of a disruption in thecontinuity of contact between packing 142 and plate 119 may be correctedby adjusting those of a spaced plurality of biasing means 126 carried bydoor 122 in the region of the gap to bias a local portion of packing 142toward plate 119 to eliminate the gap, or substantially reduce its size.Each of biasing means 126 comprises a set screw 143 threaded into atapped hole 144 extending through door 122, including channel 141, in adirection generally transversely of the plane of contact between packing142 and plate 119. Retraction of a localized portion of packing 141 fromplate 119, as to accommodate a convex outward bow of plate 119, may beaccomplished by adjusting those of biasing means 126 in the region ofthe bow away from packing 142 and thence by biasing packing 142 towardthe adjusted biasing means, as by applying force against face 142a byhand or by biasing door 122 against plate 119.

In the embodiment of FIG. 9, which is similar to that of FIGS. 7 and 8,vertically reciprocable door plate 212 is provided with an annularL-shaped member 241 which defines a channel 241a with the outer edge212a of doorplate 212. The opening of channel 241a faces toward theannular sealing surface 221 of annular member 219 which circumscribesthe opening 213 of a vestibule. Channel 241a is provided with packing242, similar to packing 142 of FIGS. 7 and 8, and similarly backed by athin flexible metal plate 245. Packing 242 extends outwardly fromchannel 241a toward member 219 and abuts against sur face 221 whendoorplate 212 is in the closed position. A local portion of packing 242may be biased toward surface 221 by one of a plurality of spaced biasingmeans 226 comprising a bolt 243 threaded through a hole in one leg ofmember 241, and extending generally transversely of doorplate 212 towardpacking 242.

The best mode known to us to carry out this invention has been describedabove in terms sufliciently full, clear, concise, and exact as to enableany person skilled in the art to make and use the same. It is to beunderstood, however, that it is contemplated that other modes of practicing the invention can be made by a skilled artisan without departingfrom the scope of the invention which is defined only by the appendedclaims.

We claim:

1. Apparatus comprising, in combination: wall means defining a vestibulehaving an opening; annular means connected to the wall means comprisingan annular plate member having a first surface circumscribing theopening; movable door member having a second surface for abuttingagainst the first surface for closing the opening; and a plurality ofbiasing means mounted on one of said members at spaced points disposedin an annular pattern circumscribing the opening for selectively biasingat least one local portion of one of said first and second surfacestoward the other of said first and second surfaces for closing anylocalized gap therebetween when the first surface is in abuttingrelationship to the second surface, each of said biasing means. beingtotally contained at one of said spaced points and operative toselectively bias a local portion independently of other of said spacedpoints.

2. Apparatus according to claim 1 wherein the annular means comprises asecond annular plate member attached to the wall means, and wherein thefirst annular plate member and second annular plate member are spacedapart from one another with the second annular plate member being spacedon the opposite side of the first annular plate member from the firstsurface; and wherein the biasing means comprises means carried by theannular means for biasing the first annular plate member away from thesecond annular plate member toward the second surface thereby locallyincreasing the space between the first annular plate member and thesecond annular plate member.

3. Apparatus according to claim 2 wherein each of the biasing meanscomprises a port in the second annular plate member; a stud extendingfrom the first annular plate member through the port; and a tighteningnut on the end of the stud for biasing the first annular plate membertoward the second annular plate member.

4. Apparatus according to claim 3 and further comprising a bolt threadedthrough second annular plate member and extending toward the firstannular plate member for biasing the first annular plate member awayfrom the second annular plate member.

References Cited by the Examiner UNITED STATES PATENTS 1,765,642 6/1930Wilhelm 110173 X 2,040,887 5/1936 Van Ackeren 110l73 X 2,507,360 5/ 1950Wicks 110173 2,662,053 12/1953 Brown 110173 X FOREIGN PATENTS 893,24410/ 1953 Germany. 868,298 5/ 1961 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner.

1. APPARATUS COMPRISING, IN COMBINATION: WALL MEANS DEFINING A VESTIBULEHAVING AN OPENING; ANNULAR MEANS CONNECTED TO THE WALL MEANS COMPRISINGAN ANNULAR PLATE MEMBER HAVING A FIRST SURFACE CIRCUMSCRIBING THEOPENING; MOVABLE DOOR MEMBER HAVING A SECOND SURFACE FOR ABUTTINGAGAINST THE FIRST SURFACE FOR CLOSING THE OPENING; AND A PLURALITY OFBIASING MEANS MOUNTED ON ONE OF SAID MEMBERS AT SPACED POINTS DISPOSEDIN AN ANNULAR PATTERN CIRCUMSCRIBING THE OPENING FOR SELECTIVELY BIASINGAT LEAST ONE LOCAL PORTION OF ONE OF SAID FIRST AND SECOND SURFACESTOWARD THE OTHER OF SAID FIRST AND SECOND SURFACES FOR CLOSING ANYLOCALIZED GAP THEREBETWEEN WHEN THE FIRST SURFACE IS IN ABUTTINGRELATIONSHIP TO THE SECOND SURFACE, EACH OF SAID BIASING MEANS BEINGTOTALLY CONTAINED AT ONE OF SAID SPACED POINTS AND OPERATIVELY TOSELECTIVELY BIAS A LOCAL PORTION INDEPENDENTLY OF OTHER OF SAID SPACEDPOINTS.